The invention concerns a sealing arrangement comprising a U-cup of a viscoplastic synthetic material, a stationary machine part, and a translatory movable machine part with an outer radius R, wherein the U-cup is disposed as a contracting joint under radial prestress between the stationary machine part and the movable machine part in a profiled section of and/or the stationary machine part, wherein the U-cup has a radially outer and a radially inner sealing lip on a high-pressure side, wherein the stationary and the movable machine parts are separated on a low-pressure side by a sealing gap width B, wherein an abutment surface of the U-cup abuts a radially oriented region of the profiled section on the low-pressure side, wherein the U-cup has an inner radius and an outer radius, wherein both in the unpressurized state and in the pressurized state, the inner radius of the U-cup in the region of the abutment surface is larger than the sum of R and B and wherein the U-cup comprises an inner surface facing the movable machine part, wherein the inner surface comprises several liquid dragging bore reliefs formed as recesses in the inner surface of the
U-cup.
Sealing arrangements having U-cups are disclosed e.g. by H. K. Müller, “Abdichtung bewegter Maschinenteile” (Sealing of movable machine parts), Medienverlag Ursula Müller, Waiblingen 1990, pages 162 pp.
If a translatory movable machine part, e.g. a piston rod, shall be hydraulically moved in a stationary machine part, leakage of the force-transmitting hydraulic liquid, e.g. oil, must be prevented. For this purpose, U-cup rod seals are used in this connection.
A U-cup according to prior art consists substantially of a basic body with cuboid cross-section and two high-pressure side sealing lips. The U-cup rests firmly in a groove of the stationary machine part, wherein the groove generally has a rectangular cross-section. Hydraulic liquid may enter into the groove space from the high-pressure side from a gap between the movable and the stationary machine part. At least the radially outer sealing lip of the U-cup is supported on the groove bottom and at least its radially inner sealing lip is supported on the movable machine part, thereby subdividing the groove space and preventing spreading of the hydraulic liquid into the low-pressure part of the groove space.
When the hydraulic liquid is pressurized, the U-cup is subjected to external forces which press it to the groove walls and the movable machine part with an increased force, thereby increasing the sealing effect of the U-cup. However, more hydraulic fluid than necessary for an efficient seal as well as low wear of the U-cup adheres to the movable machine part and is dragged from the high-pressure side to the low-pressure side of the U-cup (beyond the inner sealing lip).
Accordingly, it is the underlying purpose of the present invention to provide a highly wear-resistant sealing arrangement on the basis of a U-cup rod seal with an overall reduced leakage of hydraulic fluid.